With the continuous development of mobile communication technologies, the relay technology has been applied to public transportation vehicles moving at a high speed, for example, a high-speed train, so that high quality communication services are provided for a user equipment (UE) on the public transportation vehicles.
The relay technology refers to adding one or multiple relays between an base station and a UE so that a radio signal sent by the base station may be forwarded once or multiple times until the signal reaches the UE. Taking a simple two-hop relay as an example, the relay device divides one radio link from the base station to the UE into two radio links: a radio link from the base station to the relay device, and a radio link from the relay device to the UE. In this way, one link with poor quality is replaced by two links with good quality so that a larger link capacity and wider network coverage are obtained. In a public transportation vehicle moving at a high speed, for example, a train, the UE may access the relay device installed on the train. With high-speed moving of the train, the relay device may traverse multiple cells. When the relay device traverses multiple cells, a Donor E-UTRAN Node B (DeNB) changes. Here UTRAN stands for Universal Terrestrial Radio Access Network. Therefore, the relay device is handed over between cells, and all UEs on the train are handed over in group handover mode.
The relay device introduced between the UE and base station prolongs the delay in the handover operation. Consequently, the service interruption time of the UE controlled by the relay device is prolonged, and service continuity is poor, which reduces the quality of service.